Solid-State Imaging Device and Method of Inspecting Solid-State Imaging Device

This application is based on and claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2024-0147935, filed on Oct. 25, 2024, in the Korean Intellectual Property Office, and Japanese Patent Application No. 2024-091970, filed on Jun. 6, 2024, in the Japan Patent Office, the disclosures of which are incorporated by reference herein in their entirety.

Inventive concepts relate to, for example, a solid-state imaging device and/or to methods of inspecting and/or imaging using the solid-state imaging device.

A solid-state imaging device may, for example, receive light incident from a subject and photoelectrically convert the received light to generate an electrical signal. For example, a solid-state imaging device may include a CMOS image sensor, etc. A solid-state imaging device may perform analog-to-digital (AD) conversion processing to convert an analog signal output from a light-receiving element such as, for example, a photodiode, into a digital signal. Hereinafter, analog-to-digital conversion processing may be referred to as AD conversion processing.

A solid-state imaging device may use a technology for changing the slope (e.g., gain) of a reference signal during AD conversion processing. When the slope of the reference signal is used during AD conversion processing, the time taken to invert the magnitude relationship between the analog signal, output from a pixel, and the reference signal generated by a reference signal generation unit may be accelerated, and the time required for AD conversion processing may be shortened.

However, when the slope of a reference signal is used during AD conversion processing, if the output signal after AD conversion processing does not have linearity characteristics, correction processing for correcting the output signal may be performed. It may be advantageous to check whether the output signal after correction processing has appropriate linearity characteristics.

As a method of checking whether the output signal of a solid-state imaging device has appropriate linearity characteristics, a gradient image may be captured by the solid-state imaging device and the captured image may be checked. However, capturing the gradient image by using the solid-state imaging device may be difficult because the preparation of imaging conditions, etc. may be complicated and take time.

Meanwhile, in addition to the method of capturing the gradient image by using the solid-state imaging device, there are methods of generating the gradient image by similarly generating an analog signal (pixel signal) using a voltage source and inputting the analog signal to an AD converter. Such methods may utilize a separate power circuit (e.g., a digital to analog converter (DAC) circuit) to perform accurate inspection, and relatively increase costs.

Inventive concepts relate a solid-state imaging device capable of performing analog-to-digital (AD) conversion processing on a pixel signal output from pixels exposed at different exposure times by setting the different exposure times for each of at least one pixel row of a pixel array, and/or to methods of inspecting the solid-state imaging device. The inventive concepts may relate to a solid-state imaging device capable of relatively easily and relatively inexpensively indicating or confirming that AD conversion processing of a pixel signal, and/or signal processing after AD conversion processing, is performed appropriately and/or accurately, and/or or to methods of inspecting the solid-state imaging device.

According to some example embodiments of inventive concepts, a solid-state imaging device may include a pixel array comprising a plurality of pixels arranged oriented in a matrix; a pixel control unit configured to control operations of the plurality of pixels, the control of operations of the plurality of pixels including at least setting different exposure times for each pixel row of at least one pixel row of the pixel array; an analog-to-digital (AD) converter configured to perform AD conversion processing, the AD conversion processing including at least converting a pixel signal into a digital signal, the pixel signal being output from the pixel array, the pixel array including at least one pixel row exposed for different exposure times; and a data output unit configured to output the digital signal to the outside as image data.

According to some example embodiments of inventive concepts, a method of inspecting a solid-state imaging device, the solid-state imaging device comprising a pixel array and a ramp signal generation unit, the pixel array comprising a plurality of pixels arranged oriented in a matrix, the ramp signal generation unit configured to generate a non-linear ramp signal, may comprise controlling operations of the plurality of pixels, the controlling of operations including by setting different exposure times for each pixel row of at least one pixel row of the pixel array; performing analog-to-digital (AD) conversion processing on a pixel signal, the AD conversion processing including converting the pixel signal into a digital signal based on the non-linear ramp signal, the pixel signal being output from plurality of pixels, the plurality of pixels including pixels exposed for different exposure times based on the ramp signal; performing correction processing on the digital signal, the correction processing including correcting a non-linear output signal into a linear output signal with respect to the digital signal; and outputting the digital signal to the outside as image data after the correction processing.

According to some example embodiments of inventive concepts, a method of inspecting a solid-state imaging device, the solid state-imaging device comprising a pixel array and a ramp signal generation unit, the pixel array comprising a plurality of pixels oriented in a matrix, the and a ramp signal generation unit configured to generate a ramp signal, may comprise: controlling operations of the plurality of pixels, the controlling of operations of the plurality of pixels including at least setting different exposure times for each pixel row of at least one pixel row of the pixel array; performing analog-to-digital (AD) conversion processing on a pixel signal, the pixel signal being output from the pixels for each pixel row of at least one pixel row of the pixel array is exposed at different exposure times, the AD conversion processing being based on the ramp signal generated by the ramp signal generation unit; and outputting the pixel signal after the AD conversion processing to the outside as image data.

According to some example embodiments of inventive concepts, a method of imaging a subject using a solid state imaging device, the solid state image device including a pixel array, the pixel array including a plurality of pixels oriented in a matrix, may include performing a shutter operation on the pixel array, the shutter operation being successively performed on each pixel row from an initial pixel row to a last pixel row of the pixel array according to a certain time difference, performing a readout operation on the pixel array, the readout operation being successively performed on each pixel row from the first pixel row to the last pixel row of the pixel array according to the first time difference, performing analog-to-digital (AD) conversion on a pixel signal such that the pixel signal is converted to a digital signal, the pixel signal being output by the pixel array after the readout operation, performing correction processing on the digital signal, and outputting the corrected digital signal to the outside as image data, the image data including an image of the subject.

Hereinafter, various example embodiments of inventive concept wills be described with reference to detail with reference to the drawings. In the drawings below, the same reference numerals refer to the same components, and redundant descriptions of these components will be omitted. The size of each component in the drawings may be exaggerated for clarity and convenience of explanation. In addition, example embodiments described below are merely examples, and various modifications are possible from these example embodiments.

Hereinafter, the expressions such as, for example, “upper,” “top”, or “above” include not only those directly above in contact, but also those directly above in non-contact (e.g., and not in contact). In addition, the expressions such as, for example, “upper,” “top”, or “above” may include not only those directly above/left/right in contact, but also those directly above/left/right in non-contact. Similarly, the parts described as, for example, “lower” or “below” may include not only those directly below/left/right in contact, but also those directly below/left/right in non-contact.

A singular expression may include a plural expression unless the context clearly indicates that it is singular. In addition, when a part is said to “include,” “comprise,” or “have” a component, it means that, unless there is a specific description to the contrary, it does not exclude other components but may include other components.

In addition, the terms such as “part,” “module,” etc. described with reference to the specification mean a unit that processes one or more functions or operations, which are implemented by hardware or software or by a combination of hardware and software.

In addition, “row” and “column” merely mean directions in which pixels, etc. are arranged (e.g., oriented), and the terms “row” and “column” may be interchangeable.

In addition, “simultaneously” may include or indicate not only completely identical in time, but also cases in which, although based on control intended to be “simultaneous,” the results of which are not completely identical in time due to the influence of unevenness of elements or parasitic elements, etc.

With respect to operations constituting a method, if the order is explicitly described or there is no description to the contrary, the operations are performed in the appropriate order. It is not necessarily limited to the order described with reference to the operations. Any use of examples or exemplary terms is intended merely to explain technical ideas and is not intended to limit the scope of the claims, unless otherwise specified.

In addition, when ordinal numbers such as “first” and “second” are used in the following description, they are used for convenience and do not prescribe any order, unless specifically stated otherwise.

is a diagram illustrating a schematic configuration of a solid-state imaging device according to some example embodiments.

Referring to, a solid-state imaging devicemay include a pixel array, a pixel control unit, an analog-to-digital (AD) converter, a ramp signal generation unit, a signal processing unit, and/or a data output unit.

The pixel arraymay include a plurality of pixelsarranged (e.g., oriented) in rows and columns. Each pixelmay include a photodiode and output an analog signal according to the amount of light received by the photodiode. The pixelwill be described with reference to detail with reference to.

The pixel control unitcontrols the operation of the plurality of pixels. The pixel control unitcontrols the operation of each pixelby controlling the operation of a transistor in each pixel. The pixel control unitmay control the operation of the plurality of pixelsin a pixel row unit of the pixel array. For example, the pixel control unitmay control the operation of each pixelin a row unit of the pixelsdisposed horizontally in the pixel array. However, inventive concepts are not necessarily limited thereto.

The AD convertermay perform AD conversion processing to convert an analog signal output from the pixelsinto a digital signal. For example, the analog signal output from the pixelsmay be referred to as a pixel signal. The AD convertermay convert the analog signal into the digital signal (count value) by counting the time until the magnitude relationship between a ramp signal generated by the ramp signal generation unitand the analog signal is inverted. For example, the AD convertermay use a clock signal, and may count the clock signal until the magnitude relationship between the ramp signal and the analog signal (pixel signal) is inverted and output the clock signal as the digital signal.

The ramp signal generation unitmay generate the ramp signal. The ramp signal generation unitgenerates the ramp signal used for AD conversion processing. The ramp signal may be transmitted to the AD converter. In some example embodiments, the ramp signal generation unitis a digital-to-analog conversion (DAC) circuit and may generate, for example, a non-linear ramp signal (e.g., a ramp signal (non-linear) in). Accordingly, the output signal (for example, the digital signal) after AD conversion processing by the AD convertermay have non-linear characteristics based on a non-linear ramp signal. For example, the digital signal, which is an output signal after AD conversion processing, may have non-linear characteristics.

The signal processing unitmay perform a signal processing operation on the digital signal after AD conversion processing. The signal processing unitmay correct the output signal having non-linear characteristics after AD conversion processing. For example, the signal processing unitperforms correction processing to correct the output signal of non-linear characteristics after AD conversion processing into an output signal, for example, an output signal having linear characteristics, when counted based on a linear ramp signal. The signal processing unitmay also, for example, perform correction on any errors inherently present in the AD converter.

The data output unitoutputs the digital signal after correction processing by the signal processing unitto the outside of the solid-state imaging deviceas image data. The data output unitmay sequentially output digital signals of the plurality of pixelsto the outside in a pixel row unit of the pixel array.

The solid-state imaging devicemay further include components other than the pixel array, the pixel control unit, the AD converter, the ramp signal generation unit, the signal processing unit, and the data output unitshown in, if necessary or desired. However, inventive concepts are not necessarily limited thereto, and some of the components shown inmay be omitted from the solid-state imaging device, if necessary or desired.

is a diagram illustrating a configuration of a pixel according to some example embodiments.is a circuit diagram illustrating a schematic configuration of the pixel. The pixelofmay correspond to the pixeldescribed with reference to.

Referring to, a pixelmay include a photodiode (PD), a floating diffusion (FD), a transfer transistor, a source follower transistor, a reset transistor, and/or a selection transistor. However, inventive concepts are not necessarily limited thereto, and the pixelmay be variously implemented.

The PDgenerates charges by photoelectrically converting incident light. The FDaccumulates the charges generated by the PD. The transfer transistorcontrols the transmission of charges from the PDto the FD. The source follower transistoroutputs a voltage of a magnitude according to the amount of charges accumulated by the FD. The reset transistormay reset the charges of the floating diffusion. The selection transistorcontrols transmission of the voltage output from the source follower transistorto a column line COL.

Referring totogether, the pixel control unitcontrols the operation of each pixelby controlling the transfer transistor, the reset transistor, and/or the selection transistorof the pixel. For example, the pixel control unitmay control a shutter operation and a readout operation of the pixelsby controlling on/off of respective driving signals TG, RG, and SEL of the transfer transistor, the reset transistor, and the selection transistor. For example, the pixel control unitmay control the shutter operation and/or the readout operation of the pixelby controlling the on/off of the driving signal TG of the transfer transistor, the driving signal RG of the reset transistor, and/or the driving signal SEL of the selection transistor.

The shutter operation of a pixelis an operation of (for example, including) resetting the PDand the FD, and while the reset transistoris in a turn-on state, the transfer transistoris in a turn-on state. The readout operation of the pixelis an operation of outputting a voltage signal of the magnitude according to the amount of charges accumulated by the photodiodeto the column line COL, and while the selection transistoris in a turn-on state, the reset transistorand the transfer transistorare sequentially in a turn-on state. A period in which the transfer transistoris in a turn-off state between the shutter operation and the readout operation may, for example, correspond to an exposure period in which the charges are accumulated in the PD. Hereinafter, AD conversion processing performed by the AD converterwill be described with reference to.

is a diagram illustrating components of an AD converter according to some example embodiments.illustrates the AD converterof.

Referring to, the AD convertermay include a comparatorand/or a counter. A pixel signal and a ramp signal may be input to the comparator. The pixel signal (analog signal) may be input to one input terminal of the comparator. The pixel signal may be output from a pixel (e.g., the pixelof). The ramp signal may be input to another input terminal of the comparator. The ramp signal may be generated by, for example, a ramp signal generation unit (e.g., the ramp signal generation unitof).

The comparatorcompares the magnitude of the pixel signal of the pixelswith that of the ramp signal generated by the ramp signal generation unit. The countercounts the time until the magnitude relationship between the ramp signal generated by the ramp signal generation unitand the pixel signal is inverted. The AD convertermay output a count value counted by the counteruntil the magnitude relationship between the ramp signal and the pixel signal is inverted as a digital signal of (for example, based on) the pixel signal.

is a diagram illustrating an example of a waveform of a ramp signal generated by a ramp signal generation unit according to some example embodiments.

Referring to, the ramp signal generation unit (e.g., the ramp signal generation unitof) may generate a non-linear ramp signal having, for example, three straight lines SLto SLwith different slopes (gains) after generating a reset ramp signal. For example, the ramp signal generation unitmay generate the straight line SL, the straight line SL, and the straight line SLin an order in which they are arranged. Compared to a case where a linear ramp signal is used, when a non-linear ramp signal is used in AD conversion processing, the time until (for example, the speed at which) the magnitude relationship between the ramp signal generated by the ramp signal generation unitand the pixel signal is inverted may be accelerated, and the time required for AD conversion processing may be shortened.

An output signal (for example, digital signal) after AD conversion processing using the non-linear ramp signal may have weak linearity characteristics like the shape of the non-linear ramp signal. Accordingly, correction processing may be performed on the pixel signal after AD conversion processing (for example, on the digital signal) by a signal processing unit (e.g., the signal processing unitof) so that the output signal (for example, the digital signal) has linear characteristics.

According to a solid-state imaging device according to some example embodiments (e.g., a solid-state imaging device according to), an inspection operation of outputting image data to check whether correction processing after AD conversion processing has been appropriately performed and/or accurately performed may be performed. In some example embodiments, the solid-state imaging deviceaccording to some example embodiments may perform an imaging operation of imaging a subject and outputting image data. Hereinafter, an operation of the solid-state imaging devicewill be described with reference to detail with reference to.

is a diagram illustrating an imaging operation of a solid-state imaging device according to some example embodiments. The imaging operation may mean an operation of a solid-state imaging device (e.g., a solid-state imaging device according to solid-state imaging deviceof) imaging a subject and outputting image data.

Referring to, the vertical axis ofrepresents a row address of a pixel array (e.g., the pixel arrayof), and the horizontal axis ofrepresents time (sec). The dark solid line (Shutter) inindicates a start time of a shutter operation of each pixel row, and the light solid line (Read) indicates a start time of a readout operation of each pixel row. The shutter operation corresponds to an exposure start operation of the pixel, and the readout operation corresponds to an exposure end operation of the pixel. In some example embodiments, the solid-state imaging devicemay operate in, for example, a rolling shutter method. However, inventive concepts are not limited thereto, and the solid-state imaging devicemay operate in, for example, a global shutter method. The solid-state imaging deviceoperating in a rolling shutter method will be described with reference to.

In the imaging operation of the solid-state imaging deviceoperating in a rolling shutter method, the shutter operation and/or readout operation may be sequentially performed for each pixel row at one or more certain time differences from an initial pixel row (e.g., row number: 1) to a last pixel row (e.g., row number: 8000) of the pixel array. After a certain exposure time ET has elapsed from the start time of the shutter operation, the readout operation may be sequentially performed for each pixel row from the initial pixel row (e.g., row number: 1) to the last pixel row (e.g., row number: 8000).shows that 8000 pixel rows are included in the pixel array, but inventive concepts are not necessarily limited thereto, and the number of pixel rows may be variously implemented.

In the imaging operation of the solid-state imaging deviceaccording to some example embodiments, exposure of the same exposure time ET is performed on all the pixelswhile delaying an exposure start time for each pixel row at regular intervals from the initial pixel row to the last pixel row. For example, exposure of the same exposure time ET may be performed for each pixel row from the initial pixel row (e.g., row number: 1) to the last pixel row (e.g., row number: 8000). The pixel signal output from the pixelafter exposure may be output to the outside as image data by performing AD conversion processing and correction processing thereon. An image based on the image data is, for example, a general imaging image of a subject. Hereinafter, the inspection operation of the solid-state imaging devicewill be described with reference to.

is a diagram illustrating an inspection operation of a solid-state imaging device according to some example embodiments. The inspection operation may mean an operation of outputting inspection image data. The inspection operation may be, for example, performed in a state in which uniform light is irradiated to the pixel array. Hereinafter, the inspection image data may be referred to as an inspection image.

The vertical axis ofrepresents a row address of the pixel arrayand the horizontal axis represents time (sec). The dark solid line (Shutter) inindicates a start time of a shutter operation of each pixel row, and the light solid line (Read) indicates a start time of a readout operation of each pixel row. The shutter operation corresponds to an exposure start operation of the pixel, and the readout operation corresponds to an exposure end operation of the pixel.

Referring to, in the inspection operation of the solid-state imaging deviceaccording to some example embodiments, the shutter operation may be performed simultaneously on all pixel rows from the initial pixel row (e.g., row number: 1) to the last pixel row (e.g., row number: 8000). In some example embodiments, in the inspection operation of the solid-state imaging device, exposure of different exposure times ET may be performed on each pixel row from the initial pixel row to the last pixel row. The readout operation may be sequentially performed for each pixel row at a certain time difference from the initial pixel row to the last pixel row. For example, the exposure time ET with respect to the initial pixel row (e.g., row number: 1) may be shorter than the exposure time ET with respect to the last pixel row (e.g., row number: 8000). The shutter operation and the readout operation may be performed simultaneously on the initial pixel row, or substantially so.

In the inspection operation of the solid-state imaging deviceaccording to some example embodiments, exposure may be started simultaneously on all pixel rows, and exposure at different exposure times ET may be performed for each pixel row while delaying the exposure end time for each pixel row at certain intervals from the initial pixel row to the last pixel row. For example, the exposure time ET of the pixelof the initial pixel row may be 0, and the exposure time ET per certain time difference may be increased from the initial pixel row to the last pixel row. The exposure time ET of the pixelin the last pixel row may be the longest.

Charges may not be accumulated or substantially accumulated or the amount of accumulated charges may be relatively small in the pixelof the initial pixel row, and the amount of charges accumulated in the pixelmay increase from the initial pixel row to the last pixel row. For example, the maximum amount of charges equivalent to(corresponding to the highest luminance) may be accumulated in the pixelof the last pixel row as an electron number conversion value. However, the above-described electron number conversion value may correspond to some example embodiments, but is not necessarily limited thereto.